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| United States Patent |
5,107,629
|
|
Boyd
, et al.
|
April 28, 1992
|
Texturing of acoustical mineral fiberboard with wheel blast machine
Abstract
A method for texturing the surface of an acoustical fiberboard by utilizing
a wheel blast machine. The fiberboard is conveyed through a housing
wherein at least one first centrifugal blasting wheel throws abrasive
particles at a portion of the fiberboard surface to abrade it. A blower
provided in the housing removes spent abrasive particles thrown by the
first wheel(s), and then at least one second centrifugal blasting wheel in
the housing throws abrasive particles at the remaining untreated surface
to complete the abrasion, whereby removal of the spent particles by the
blower prevents masking of the surface and allows the formation of a
pleasing and uniform pattern over the entire fiberboard surface.
| Inventors:
|
Boyd; Alan L. (Seminole, FL);
Migliorini; Fred L. (St. Petersburg, FL)
|
| Assignee:
|
The Celotex Corporation (Tampa, FL)
|
| Appl. No.:
|
683931 |
| Filed:
|
April 11, 1991 |
| Current U.S. Class: |
451/38; 451/36; 451/37; 451/75; 451/81; 451/87; 451/94 |
| Intern'l Class: |
B24B 001/00 |
| Field of Search: |
51/420,317,318,319,326,410,417,418,424,425,426,428,431,432
|
References Cited
U.S. Patent Documents
| 2338591 | Jan., 1944 | Learmonth | 51/9.
|
| 2448316 | Aug., 1948 | Lesavoy | 51/14.
|
| 2455514 | Dec., 1948 | Mead | 51/8.
|
| 2777256 | Jan., 1957 | Paasche | 51/14.
|
| 2952100 | Sep., 1960 | Pelley | 51/14.
|
| 2993309 | Jul., 1961 | Barnes et al. | 51/14.
|
| 3117403 | Jan., 1964 | Jack et al. | 51/311.
|
| 3269066 | Aug., 1966 | Straub | 51/319.
|
| 3405481 | Oct., 1968 | Harper | 51/9.
|
| 3473941 | Oct., 1969 | Hemphill | 117/5.
|
| 3540155 | Nov., 1970 | Walker et al. | 51/9.
|
| 3597928 | Jul., 1971 | Terentiev et al. | 264/87.
|
| 3731432 | May., 1973 | Carpenter, Jr. | 51/426.
|
| 4001977 | Jan., 1977 | Schrader | 51/15.
|
| 4087285 | May., 1978 | Kurtz | 106/52.
|
| 4093754 | Jun., 1978 | Parsons | 427/259.
|
| 4174591 | Nov., 1979 | Dupre et al. | 51/16.
|
| 4303703 | Dec., 1981 | Maron | 427/272.
|
| 4476655 | Oct., 1984 | Ansbaugh | 51/215.
|
| 4566230 | Jan., 1986 | Carpenter, Jr. | 51/420.
|
| 4597928 | Jul., 1986 | Terentiev | 264/236.
|
| Foreign Patent Documents |
| 0045018 | Feb., 1983 | EP | 134/7.
|
Primary Examiner: Rachuba; M.
Attorney, Agent or Firm: Vanecek; Charles W.
Parent Case Text
This is a continuation-in-part of Application Ser. No. 07/603,644, filed
Oct. 26, 1990, now abandoned, which is a continuation of Application Ser.
No. 07/433,813, filed Nov. 9, 1989, now abandoned.
Claims
We claim:
1. A method of decoratively texturing the surface of an unmasked fiberboard
which comprises:
(a) conveying the fiberboard in a horizontal position through a closed
housing having entry and exit slots for the fiberboard, and
(b) decoratively texturing the top surface of the fiberboard while the
fiberboard is within the housing by:
(i) discharging particulate material downwardly against a region of the
surface of the fiberboard to abrade the surface, a portion of the spent
particulate material thereby being deposited on the surface of the
fiberboard,
(ii) blowing the spent particulate material off the surface, and
(iii) discharging additional particulate material downwardly against the
surface to complete the abrasion, whereby removal of the spent particulate
material from the first discharge prevents masking of the surface and
contributes to the formation of a decorative and uniform pattern over the
entire fiberboard surface.
2. The method of claim 1 wherein the spent particulate material is blown
off the surface of the fiberboard by air directed angularly downwardly
onto the fiberboard.
3. The method of claim 1 wherein the fiberboard is conveyed through the
housing at a speed of about 150 to 180 lineal feet per minute.
4. The method of claim 3 wherein the fiberboard has a width of about 24
inches to 52 inches.
5. The method of claim 1 wherein the particulate material in step (b)(i) is
thrown by at least one first centrifugal blasting wheel mounted in the
roof of the housing to cause a portion of the surface to be uniformly
impacted, and the particulate material in step (b)(iii) is thrown by at
least one second centrifugal blasting wheel mounted in the roof of the
housing downstream from the first wheel or wheels to cause the remaining
untreated surface to be uniformly impacted.
6. The method of claim 5 wherein the spent particulate material in step
(b)(ii) is blown off the surface by a blower means mounted in the roof of
the housing and located between two baffles mounted in the roof of the
housing, one baffle being located between the first centrifugal blasting
wheel or wheels and the blower means and the other baffle being located
between the blower means and the second centrifugal blasting wheel or
wheels.
7. The method of claim 6 wherein the spent particulate material is blown
off the surface of the fiberboard by air directed angularly downwardly
onto the fiberboard.
8. The method of claim 7 wherein the fiberboard whose surface is to be
textured is formed by a wet process comprising depositing a water slurry
of the board-forming ingredients upon a moving wire screen for drainage
therefrom of water to form a wet felt, and consolidating and drying the
wet felt.
9. The method of claim 1 wherein the particulate material in step (b)(i) is
thrown by a first pair of centrifugal blasting wheels mounted in the roof
of the housing and staggered in a longitudinally spaced apart relation and
in a laterally spaced apart relation to cause regions at the outer edges
of the surface to be uniformly impacted, and the particulate material in
step (b)(iii) is thrown by a second pair of centrifugal blasting wheels
mounted in the roof of the housing downstream from the first pair and
staggered in a longitudinally spaced apart relation and in a laterally
spaced apart relation to cause the interior region of the surface to be
uniformly impacted.
10. The method of claim 9 wherein the particulate material is a member
selected from the group consisting of glass shot, plastics, metal shot or
grit, walnut shells, pecan shells, corn husks, and peach pits.
11. The method of claim 9 wherein the spent particulate material in step
(b)(ii) is blown off the surface by a blower means mounted in the roof of
the housing and located between two baffles mounted in the roof of the
housing, one baffle being located between the first pair of centrifugal
blasting wheels and the blower means and the other baffle being located
between the blower means and the second pair of centrifugal blasting
wheels.
12. The method of claim 11 wherein the spent particulate material is blown
off the surface of the fiberboard by air directed angularly downwardly
onto the fiberboard.
13. The method of claim 12 wherein the air is directed angularly downwardly
from an air knife.
14. The method of claim 12 wherein the air is directed angularly downwardly
from an elongated pipe having a slit and mounted in the roof of the
housing to extend above the production line and from side to side thereof.
15. The method of claim 12 wherein the fiberboard is conveyed through the
housing at a speed of about 150 to 180 lineal feet per minute.
16. The method of claim 15 wherein the fiberboard has a width of about 24
inches to 52 inches.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for producing an
acoustical fiberboard, and more particularly is directed to the surface
texturing of a mineral ceiling panel with a wheel blast machine.
2. Description of the Prior Art
Shaped products made from fibers and a binder, which are typically
acoustical in nature, i.e., capable of attenuating sound, are well known
in the art and are widely used today. Examples of such shaped products
include ceiling panels and tiles, wall boards, screen dividers,
construction panels, and the like. The conventional process for making
these products involves use of a fourdrinier-type machine wherein an
aqueous mixture comprising the fiber and binder is cast on a forming
screen, and subsequently consolidated and dewatered. Normally, the formed
board is passed to an oven for final drying.
A wide variety of processes have been employed in the past to produce a
textured surface on these fiberboards, including cutting, routing,
abrading, using adhesive inks or templates, etc. Frequently, it has been
difficult to texture the boards without considerably weakening them or
otherwise disadvantageously affecting them. A particular problem has been
to carry out the texturing in such a way that a pleasing and uniform
pattern is created on the board while the overall board properties are
preserved. This problem is particularly exacerbated when the boards are
extra wide and/or produced at high line speeds.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved
method and apparatus for decoratively texturing the surface of a
fiberboard, whereby a pleasing and uniform pattern is formed without
substantially diminishing the board's physical properties.
It is another object of the present invention to provide a method of
decoratively texturing fiberboard, whereby a pleasing and uniform surface
pattern is produced on extra wide boards being rapidly conveyed along a
production line.
It is still another object of the present invention to provide a
fine-textured fiberboard which is characterized by a combination of
desirable physical properties, including good strength and
sound-absorption properties and a highly decorative and uniform surface
pattern.
Other objects and advantages of the present invention will become apparent
to those skilled in the art when the instant disclosure is read in
conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The present invention provides a method for making an acoustic fiberboard,
preferably a mineral ceiling panel, in which the surface of the board is
textured by a wheel blast machine. The board product may be formed
continuously by conventional wet processes wherein a water slurry of the
board-forming ingredients is deposited upon a moving wire screen. The
invention may also involve an operation whereby boards are formed in a
cast process without water drainage from the product. After consolidation
and drying, the board is abraded on either one of its two major surfaces.
The wheel blast machine comprises in sequence a first abrasive discharging
means, a blower means and a second abrasive discharging means. As the
dried board is conveyed through an abrading zone, abrasive particles are
thrown by the first discharging means against the board to abrade its top
surface. After thus impacting the surface of the board, spent abrasive
particles collected on the board surface are blown therefrom by the blower
means, thereby removing these particles from the path of the next
collection of particles from the second discharging means.
More particularly, the present invention provides an apparatus for applying
particulate material to the surface of a fiberboard to be provided with a
decorative pattern comprising:
(a) a closed housing having entry and exit slots for the fiberboard;
(b) means for conveying the fiberboard to be treated through said housing
in a horizontal position;
(c) a first abrasive discharging means disposed within the housing above
the surface of the fiberboard to be treated for applying particulate
material to the surface thereof;
(d) a blower means for removing spent particulate material collected on the
surface of the fiberboard after discharge from the first abrasive
discharging means; and
(e) a second abrasive discharging means disposed within the housing above
the surface of the fiberboard for further treatment of the surface with
particulate material.
The first and second abrasive discharging means each advantageously
comprise at least one centrifugal blasting wheel mounted in the roof of
the housing to cause a portion of the fiberboard surface to be uniformly
impacted. The second discharging means is located downstream along the
production line from the first such means in order to abrade the remaining
fiberboard surface untreated by said first means. Air blown from a device
such as an air knife removes spent particulate material left on the
surface after its abrasion by the first discharging means. This removal
allows the production of a highly decorative and uniform pattern on the
surface of the fiberboard.
Advantageously, to the upstream side of the air blower device and between
this device and the first abrasive discharging means is a baffle which is
mounted transversely to the longitudinally extending conveyor means and
forms a complete partition across the housing except for a narrow
rectangularly-shaped opening below the baffle's lower edge for conveyance
of the fiberboard through the housing. A similar baffle is suitably
mounted to the downstream side of the air blower device and between the
device and the second abrasive discharging means to likewise partition the
housing except for a bottom opening for fiberboard passage. These two
partitions help to lessen interference by the abrasive thrown by the
discharging means with the air cleaning operation.
DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to the accompanying
drawings in which:
FIG. 1 a diagrammatic, side elevational view of an apparatus for carrying
out the method of the present invention;
FIG. 2 is an enlarged cross-sectional view of the wheel blast machine shown
in FIG. 1;
FIG. 3 is an enlarged top view of the wheel blast machine shown in FIG. 2,
with certain parts being broken away for clarity; and
FIG. 4 is an enlarged perspective view of an air knife for removing
abrasive particles.
DETAILED DESCRIPTION OF THE INVENTION
In carrying out the invention, a fiberboard sheet material, which may
comprise inorganic and/or organic fibrous material and preferably consists
of mineral fibers, a binder and the other board-forming ingredients, is
produced in a conventional manner, such as on a wet board forming machine,
e.g., a Fourdrinier or a cylinder machine. Referring now to FIG. 1, there
is shown a machine chest 1 containing water to which the mineral fibers,
such as conventionally felted mineral wool, are first added. Then the
other ingredients, which advantageously consist of aqueous suspensions of
perlite and optionally clay, of starch, and of paper, are added to the
machine chest. The machine chest agitator 2 is suitably operated to keep
the slurry stirred up so that the ingredients are uniformly distributed
throughout the slurry. The solids content of the slurry may be from about
2 to 8 weight %.
In an advantageous embodiment of the invention, the fiberboard is produced
from a slurry containing mineral fibers (e.g., mineral wool) which are
nodulated during wet mixing of the slurry's ingredients. To bring about
substantial formation of nodulated wool upon mixing of the slurry, the
consistency must be sufficiently high, e.g., about 5 to 8, preferably 5.5
to 8, and more preferably 6 to 7.5 weight %. The formation of nodules of
mineral fiber during mixing of the slurry may be brought about as
described in U.S. Pat. application Ser. No. 210,446, filed Jun. 23, 1988,
the disclosure of which application is hereby incorporated by reference.
The rate and duration of agitation for forming an appropriate content of
nodulated wool in the slurry can be readily determined through routine
experimentation. Generally, the slurry is mixed for about 10 to 60 minutes
by means of a rotary agitator (impeller) revolving at a rate of about 100
to 150 revolutions per minute. Alternatively, the mineral wool may be
introduced to the slurry in the form of pellets of previously nodulated
mineral wool.
After the slurry is agitated sufficiently to uniformly distribute the
solids and, when appropriate, to nodulate the wool, the slurried
composition is transferred by pump 3 through pipe 4 to head box 5. The
slurry is subsequently deposited on Fourdrinier wire 7 through orifice 6
of head box 5. The first section 8 of the Fourdrinier wire permits free
drainage of water from the material and further drainage is promoted by
suction boxes 9 in section 10. As the slurry is brought in contact with
the Fourdrinier machine and water of the slurry drains therefrom, a wet
felted mat of the mineral fiber composition forms on the machine. The wet
laid mat is dewatered by the Fourdrinier machine to a solids content of
about 20 to 40 weight percent.
The partially dried material is then prepressed to a thickness of about 0.4
to 0.8 inch by a plurality of press rolls 11. It will be appreciated that
a single set of press rolls could be employed if desired. After being
pressed, the sheet product will generally have from about 60 to about 75%
water. A coating may be applied to the pressed mat by means of feed-pipe
13 and coater 14.
After passing through press rolls 11, the wet mat is transferred into dryer
12. At the outlet of the dryer, there is obtained a board 15 having a
moisture content of about 1.0%. The board is cut into smaller panels by
saw arrangement 16. Dried boards having widths of 24 in. or more, e.g., 24
to 52 in., can be formed for texturing by the wheel blast machine of the
invention. The dried product can be subjected to any suitable conventional
finishing apparatus, depending on the applications for which it is
intended. Such apparatuses may include applicators for applying coatings
to protect and/or decorate the product surface, such as bevel coaters,
finish spray coaters, printers, multi-color decorative coaters, and the
like, and further drying equipment.
A fine-textured appearance is created on one of the two major surfaces of
the dried board by the wheel blaster 17 of the invention. The board may be
advantageously turned over by an inverter 18 to present the smooth screen
side for surface treatment. The board is continuously passed by suitable
conveyor means (e.g., conveyor rollers 19) through the wheel blast machine
located on the production line. The housing 20 of the machine has inlet
and outlet openings 25 and 26 for the board. The process can be run at a
line speed of up to 200 lineal feet per minute. However, for optimum
pattern uniformity, the line speed through the wheel blast machine
generally should be about 150-180 lfpm. It is, of course, understood that
the speed of the line can be readily adjusted so that the entire board
surface will be uniformly subjected to the action of the abrasive spray
from the wheel blaster. Even at quite high line speeds, the present
invention makes it possible to produce pleasing and uniform patterns on
boards which are much wider than conventionally textured boards. Whereas a
typical width of a conventionally textured board is about 2 ft., boards
having widths up to 52 in. or more can be readily textured in accordance
with the present invention.
Referring now to FIGS. 2 and 3, it will be seen that conveyor rollers 19
carry fibrous board 15 through the housing 20 of the wheel blast machine
to abrade and thereby decoratively texture the board surface with abrasive
material 21 propelled by first abrasive discharging means 22. The first
abrasive discharging means advantageously comprises one or more roof
mounted centrifugal blasting wheels 22 located within the blasting chamber
directly above the conveyor means for directing the abrasive material
downwardly upon the board as it passes through the chamber. When more than
one blasting wheel is employed, such as the two shown in FIGS. 2 and 3,
the wheels 22.sup.a, 22.sup.b preferably are staggered in a longitudinally
spaced apart relation and in a laterally spaced apart relation to cause
the top surface of the board to be uniformly impacted by the abrasive
particles centrifugally thrown by the wheels, preferably at an acute angle
with respect to said board surface. The desired effect of the spacing is
that abrasive thrown by the first wheel onto the board will ricochet
without passing through the path of abrasive particles thrown by the next
wheel thereby to minimize interferences with the particles thrown at the
surfaces of the boards and also to avoid undesirable cushioning effects.
Wheels 22.sup.a, 22.sup.b are advantageously located so as to abrade the
outer edges of the board.
The machine includes a second abrasive discharging means located within the
blasting chamber downstream from the first such means. The second abrasive
discharging means advantageously comprises one or more roof mounted
centrifugal wheels 23 (two shown in FIGS. 2 and 3) similarly spaced for
uniform treatment and texturing of the board surface. Wheels 23.sup.a,
23.sup.b are suitably mounted to treat the interior portion of the board.
The throwing wheels may be of conventional type described in the art, and
can be obtained from Wheelabrator-Frye, Inc.
The surface-treating material 21 may be any abrasive capable of texturing
the surface of the board. Both "heavy" abrasives (e.g., metal grit or
shot) and "light" abrasives, which are of softer materials than the former
type, may be used. "Light" abrasives include such items as glass shot,
plastics, walnut shells, pecan shells, corn husks, peach pits, etc.
Typically, the surface abrasion removes about 0.01-0.04, preferably
0.025-0.035, inch of the board surface in producing the desired look.
Depending on factors such as the type of abrasive and board being treated
as well as the spatial relationship of the wheels and board, the wheels
can be operated at various speeds, such as from about 1800 to 3600 rpm.
Abrasive granules thrown by the first discharging means against the upper
surface of board 15 rebound therefrom and collect inside cabinet 20 and
disadvantageously on the board surface. If this spent blast medium is not
removed from the surface of the board prior to the surface's exposure to
another discharging means, an unacceptable condition known as "masking"
occurs. This phenomenon results from blast medium covering the surface of
the board and then being hit by subsequently thrown blast medium. The
effect is lower relative abrasion from the second discharging means and,
even when abrasion is evident, the character of the abrasion changes such
that the texture of the masked area appears different from surrounding
areas when painted, presenting an undesirably variable appearance.
A blower means disposed between the first and second abrasive discharging
means removes from the board surface the spent abrasive particles thrown
by the former means before exposure of the surface to the second abrasive
discharging means. The blower means advantageously comprises a roof
mounted device which supplies air under pressure to blow the spent
abrasive off the board surface. As illustrated in FIGS. 2 to 4, air under
pressure is directed from a suitable source, not shown, to a manifold 24,
whereby air is directed downwardly at an angle of less than 90 to gently
sweep the abrasive material from the surface. The air manifold may, for
example, consist of a compressed air knife or a manifold connected to a
centrifugal blower. In a preferred embodiment, the air is directed
angularly downwardly onto the fiberboard to blow the abrasive particles
laterally outwardly from its surface whereby the particles are displaced
laterally beyond the board where they can settle downwardly for return by
any suitable means to the chamber supplying the blast wheels to again be
used. An especially suitable device for supplying air is the FIG. 4
embodiment comprising an elongated pipe 24 having a slit and mounted in
housing 20 to extend above the production line and from side to side
thereof.
As shown in FIGS. 1 to 3, baffles or partitions 27 and 28, in a generally
parallel configuration, suitably are rigidly mounted on the roof of
cabinet 20 and located to either side of blower device 24. The baffles
help to reduce interference between the abrasive thrown by the first and
second discharging means. They also help to lessen interference between
the abrasive thrown by the discharging means and the cleaning operation of
the intervening blower means. Each baffle suitably comprises a metal plate
which extends downwardly from the roof and laterally from side to side of
the cabinet, with its lower horizontal edge spaced a short distance above
the open channel for the conveyor line extending from entrance 25 to exit
26 across the bottom of housing 20.
A final blow-off device, not shown, is located within housing 20 to remove
residual abrasive material before conventional finishing of the boards.
From the above description it is seen that the present invention provides a
method and apparatus whereby fiberboard surfaces may be rapidly and
economically textured. In addition, the invention is seen to provide a
method and apparatus for texturing fiberboard with abrasive particles by
which method and apparatus the surface of the fiberboard may be uniformly
and decoratively abraded without complications from spent abrasive on the
board surface. The previous practice of removing spent abrasive from a
treated surface by employing wipers made of rubber or similar material
would be unacceptable. The dragging of these wipers across the abraded
surface to scrape off used blast medium would leave marks on the
fiberboard and result in product rejects.
The present invention is further illustrated by the following example in
which all percentages are by weight.
EXAMPLE
This example illustrates with reference to the drawings the production of
textured fiberboard in accordance with the present invention.
The formulation utilized in manufacturing the product consists of the
following ingredients in the listed percentages by weight:
______________________________________
Ingredient %
______________________________________
Mineral Wool 65.0
Perlite 21.5
Newsprint 4.0
Starch 9.5
Retention Aid 0.05
______________________________________
The ingredients were diluted with water to form a slurry in machine chest
1. Wet mixing of the slurry, which had a stock consistency of 7 wt. %,
nodulated the mineral wool. The slurry was transformed to head box 5 and
next deposited on Fourdrinier wire 7. The slurry was dewatered in a
conventional manner on the Fourdrinier machine to form a wet felt or mat
of interlocked fibers. The partially dewatered fibrous mat was next passed
through a press section comprising pressing rolls 11, which densified the
mat and provided a wet mat of uniform thickness (about one inch) with a
moisture content of about 65%. After leaving the press section, the wet
mat was conveyed to dryer 12.
After being dried, the board product was subjected to various conventional
finishing steps, which included cutting into appropriate sizes and
cleaning. After being flipped over by inverter 18, the board product was
then abraded on the screen side by wheel blaster 17 and this side was
coated to produce textured fiberboards of the invention.
Texturing of the boards was accomplished under the following conditions:
______________________________________
Line Speed 160 lfpm
Wheel Speed 2400-2600 rpm
Wheel Load 18 .+-. 1 amps
Board Thickness 0.030"-0.040"
Removal
______________________________________
Board products made in accordance with the foregoing procedure had the
following average physical properties:
______________________________________
Thickness, in. 0.700-0.750
Density, lb/cu. ft.
14.0-15.5
Transverse 19.0-25.0
Strength, lb
NRC .60-.70
______________________________________
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